Many phosphorus-containing low molecular weight compounds and polymers are known to be useful corrosion inhibitors for water treatment applications, such as in cooling towers and boilers. See, for example, U.S. Patent Publication No. 2007/0287858. (Poly)isopropenylphosphonic acid and its variants are also useful for scale inhibition. See, for example, U.S. Pat. Nos. 5,512,183, 5,519,102 and 5,594,084, as well as U.S. Patent Publication No. 2005/082793.
Thus, polymers made from phosphoalkyl (meth)acrylate monomers, which are esters, are well known for their scale and corrosion inhibiting properties. However, the carbonyl ester bonds of the phosphoalkyl (meth)acrylate-containing polymers undergo notable deterioration under high temperature conditions (i.e., even below 100° C.) because the ester bond is often not stable under such conditions. See International Journal of Chemical Kinetics, vol 22(5), pp 431, 2004 and Macromolecules, vol 31(23), pp. 8063, 1998. On the other hand, the amide bond of phosphoalkyl (meth)acrylamide-containing polymers should be stable up to much higher temperatures (i.e. more than 250° C.). See, Polymer Degradation and Stability, vol 91, pp. 21, 2006. It is common knowledge that the amides have higher hydrolytic stability than the esters under wider pH and temperature conditions, including room temperature and much higher. Water treatment and oil field applications, for example, often present high temperatures such as up to 250° C. (see The Chemical Treatment of Boiler Water, pp. 140, Chemical Publishing Co., 1981) and/or pressure conditions such as up to 10000 pounds per square inch (psi) (i.e., about 68.9 MPa) (see Oilfield Water Technology, pp. 14, NACE International, 2006). Thus, a novel polymeric scale and corrosion inhibitor that provides robust performance in such extreme conditions in aqueous or organic solvent solutions is required.
Many (meth)acrylamide phosphorus monomers and polymers have been developed for successful application in adhesives, coatings and anti-corrosive films. See, European Patent No. EP 0516346 B1 and International Patent Application Publication No. WO 2007/006648 A1.
Additionally, phosphonated amide monomers having high electrolytic group density and improved conductivity are disclosed in U.S. Pat. No. 7,452,487 for use in conductive resins, proton-conductive polymer electrolyte membranes and coating agents.
However, no one has recognized the benefits to be obtained by using phosphorus-containing amide-based polymers in high temperature and/or pressure conditions such as water treatment and oilfield applications.
Polymer chemistry with a combination of pendant carboxylate and phosphate/phosphonate groups, for example polymers comprising phosphoalkyl (meth)acrylamide monomers, should perform well as both scale and corrosion inhibitor. The present invention provides such polymers which should demonstrate both corrosion and scale inhibition properties in single polymer chemistry with good thermal and pressure stability.